/*
 * Copyright (C) 2012 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.reflect;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.Beta;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableList;

import java.lang.annotation.Annotation;
import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.AnnotatedType;
import javax.annotation.CheckForNull;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Represents a method or constructor parameter.
 *
 * @author Ben Yu
 * @since 14.0
 */
@Beta
@ElementTypesAreNonnullByDefault
public final class Parameter implements AnnotatedElement
{

    private final Invokable<?, ?> declaration;
    private final int position;
    private final TypeToken<?> type;
    private final ImmutableList<Annotation> annotations;
    private final AnnotatedType annotatedType;

    Parameter(
            Invokable<?, ?> declaration,
            int position,
            TypeToken<?> type,
            Annotation[] annotations,
            AnnotatedType annotatedType)
    {
        this.declaration = declaration;
        this.position = position;
        this.type = type;
        this.annotations = ImmutableList.copyOf(annotations);
        this.annotatedType = annotatedType;
    }

    /**
     * Returns the type of the parameter.
     */
    public TypeToken<?> getType()
    {
        return type;
    }

    /**
     * Returns the {@link Invokable} that declares this parameter.
     */
    public Invokable<?, ?> getDeclaringInvokable()
    {
        return declaration;
    }

    @Override
    public boolean isAnnotationPresent(Class<? extends Annotation> annotationType)
    {
        return getAnnotation(annotationType) != null;
    }

    @Override
    @CheckForNull
    public <A extends Annotation> A getAnnotation(Class<A> annotationType)
    {
        checkNotNull(annotationType);
        for (Annotation annotation : annotations)
        {
            if (annotationType.isInstance(annotation))
            {
                return annotationType.cast(annotation);
            }
        }
        return null;
    }

    @Override
    public Annotation[] getAnnotations()
    {
        return getDeclaredAnnotations();
    }

    /**
     * @since 18.0
     */
    // @Override on JDK8
    @Override
    public <A extends Annotation> A[] getAnnotationsByType(Class<A> annotationType)
    {
        return getDeclaredAnnotationsByType(annotationType);
    }

    /**
     * @since 18.0
     */
    // @Override on JDK8
    @Override
    public Annotation[] getDeclaredAnnotations()
    {
        return annotations.toArray(new Annotation[0]);
    }

    /**
     * @since 18.0
     */
    // @Override on JDK8
    @Override
    @CheckForNull
    public <A extends Annotation> A getDeclaredAnnotation(Class<A> annotationType)
    {
        checkNotNull(annotationType);
        return FluentIterable.from(annotations).filter(annotationType).first().orNull();
    }

    /**
     * @since 18.0
     */
    // @Override on JDK8
    @Override
    public <A extends Annotation> A[] getDeclaredAnnotationsByType(Class<A> annotationType)
    {
        @Nullable
        A[] result = FluentIterable.from(annotations).filter(annotationType).toArray(annotationType);
        @SuppressWarnings("nullness") // safe because the input list contains no nulls
        A[] cast = (A[]) result;
        return cast;
    }

    /**
     * @since 25.1
     */
    // @Override on JDK8
    public AnnotatedType getAnnotatedType()
    {
        return annotatedType;
    }

    @Override
    public boolean equals(@CheckForNull Object obj)
    {
        if (obj instanceof Parameter)
        {
            Parameter that = (Parameter) obj;
            return position == that.position && declaration.equals(that.declaration);
        }
        return false;
    }

    @Override
    public int hashCode()
    {
        return position;
    }

    @Override
    public String toString()
    {
        return type + " arg" + position;
    }
}
